A population of neurons in the arcuate nucleus of the hypothalamus expresses proopiomelanocortin (POMC), a polypeptide precursor that when cleaved yields alpha-melanocyte-stimulating hormone (alpha-MSH) and beta-endorphin (beta-end). These products are involved in the regulation of many homeostatic functions such as reproduction, fluid balance, appetite, stress and motivation. Although, it is well established that estrogen affects POMC gene expression, the molecular mechanisms have not been elucidated. This proposal aims to investigate the molecular mechanisms of estrogen action on the arcuate POMC neurons leading to increased release of alpha-MSH and beta-end. Preliminary microarray results comparing gene expression changes in the hypothalamus showed the upregulation of PI3 kinase p55gamma, which is part of the PI3-kinase signaling pathway. Using single-cell reverse-transcription PCR and in situ hybridization, I will determine if PI3Kp55gamma is localized in POMC arcuate neurons. Second, I will validate the microarray finding that PI3Kp55gamma is regulated by estrogen using RNase protection assays and quantitative real-time PCR. Finally, I will determine the function of the PI3K pathway in estrogen signaling in POMC arcuate neurons using whole-cell recordings.